Question 1
Paper 2Medium6 marksAn investigation compares the ionic solids magnesium oxide, MgO, and calcium oxide, CaO. Both have the same arrangement of ions in their lattices. The ionic radii for ions in this arrangement are shown below.
| Ion | Ionic radius / pm |
|---|---|
| Mg²⁺ | 72 |
| Ca²⁺ | 100 |
| O²⁻ | 140 |
(a)[2]
Explain why solid CaO does not conduct electricity but molten CaO does.
(b)[2]
Use the data to predict which oxide has the larger magnitude of lattice enthalpy. Explain your prediction.
(c)[2]
Hence, identify which oxide is expected to be less volatile. Explain your answer.